#include <iostream>
using namespace std;
void GET_SUM(int n,int* sum)
{
    int i=1;
    for(i=1;i<=n;i++)
    {
        *sum+=i;
    }
}
int main() {
    
    int n;
    cin >> n;
    int sum = 0;
    
    // write your code here......
    
    GET_SUM(n,&sum);
    cout << sum << endl;
    
    return 0;
}